Brace yourself. After decades spent tackling volcanoes, aliens, earthquakes, asteroids and every other disaster imaginable, Hollywood has turned its attention to one of the hottest scientific and political issues of the day: climate change.

No one is pretending the forthcoming film "The Day After Tomorrow" is anything but implausible: In the $125 million movie, global warming triggers a cascade of events that practically flash freeze the planet.

It's an abruptness no one believes possible, least of all the filmmakers behind the 20th Century Fox release. "It's very cinematic to choose the worst-case scenario, which we did," said co-screenwriter Jeffrey Nachmanoff.

Nonetheless, scientists are embracing the movie, unusual for those whose stock in trade is fact.

"My first reaction was, 'Oh my God, this is a disaster because it is such a distortion of the science. It will certainly create a backlash,"' said Dan Schrag, a Harvard University paleoclimatologist. "I have sobered up somewhat, because the public is probably smart enough to distinguish between Hollywood and the real world."

He now hopes the movie will do for interest in global warming what "Jurassic Park" did for dinosaurs.

In the new movie, due for release Memorial Day weekend, global warming melts the polar caps, sending torrents of fresh water into the world's salty oceans. That flood in turn chills a major current in the north Atlantic and tips the planet into a new Ice Age.

Quickly unleashed is every type of violent weather that filmmakers ke a movie that goes on for 10,000 years," Patzert said.

Scripps Institution of Oceanography marine physicist Tim Barnett, who's seen an extended trailer of the film, said even slower-moving change can wreak massive havoc.

Scientists point out that even subtle changes in precipitation patterns can have drastic effects on civilizations unable to pick up and move, wholesale, their farms and cities.

Most scientists agree that climate change is occurring and that human activity - most notably, the burning of fossil fuels - has an effect. Debate continues among politicians.

The Bush administration withdrew U.S. support for the 1997 Kyoto Protocol, a global effort to reduce carbon dioxide emissions. Instead, it has called for industry to voluntarily reduce emissions and for more scientific research.

Last year, the administration was criticized for ordering a major rewrite of an Environmental Protection Agency assessment of climate change. The revised version deleted references to the health and environmental risks posed by rising global temperatures.

At first, NASA reacted to the movie by ordering government scientists not to discuss it with the media. The space agency later "clarified" its instructions, saying it did not want to muzzle scientists, some of whom had said officials were trying to limit discussions of global warming because Bush had called for more research.

In the movie, human activity helps trigger the runaway cascade of climate events. Its toll is illustrated in part by the refugees who, in a wry reversal of current immigration patterns, escape the deep freeze by streaming south across the U.S. border with Mexico.

"What happens will frankly be worse than what they show, in the long run. Our lives and all our systems will get stretched and stretched and pushed and pushed," Barnett said. "The conflicts that will come up will be remarkable."

The movie also has mobilized activists, who are seizing on it as an occasion to spark public discussion about a subject they feel is getting short shrift from the public and policy-makers alike. "The Day After," a similarly titled 1983 television movie that dealt with the aftermath of nuclear war, engendered similar debate.

Moveon.org, the San Francisco-based liberal advocacy group, is organizing a town hall meeting to coincide with the movie's New York City premiere later this month. Former Vice President Al Gore, comedian and author Al Franken and environmentalist Robert F. Kennedy Jr. are among those expected to attend.

"Millions of people will be coming out of theaters on Memorial Day weekend, asking the question, 'Could this really happen?' I think we need to answer that question," Gore said in a statement.

The group's members also plan to distribute leaflets at theaters around the country when the movie is released.

"To have a major studio release of a movie tackling a serious issue is a terrific opportunity for Americans to start talking about the reality of the problem, what can be done about it and the enormous threat that President Bush is not dealing with," said Peter Schurman, Moveon.org's executive director.

Producer Mark Gordon hopes his movie will make people think. He stressed it wasn't made to suit an agenda, but he clearly reveled in the stir it's caused.

"From the box-office point of view, controversy is good. It makes people talk about it," he said. "You couldn't buy this kind of publicity."